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Ocean Watch

By Susan Scott

Friday, June 7, 2002



Wrasses worth watching,
and they are easy to find

After a bumpy-water dive on the North Shore last week, I asked one of my friends what he saw. "Wrasses," he said. "Lots of wrasses."

This isn't surprising. Whether you're in rough water or calm, clear or murky, deep or shallow, you'll almost always see some wrasses. Hawaii hosts 43 species, more than any other shore fish here. Thirteen of those are found nowhere else in the world.

But just because they're common doesn't mean they're boring. For years the wrasse family's widely varying colors, shapes and character traits have kept biologists on their toes.

One of the most remarkable aspects of wrasse biology is their sex life. Female wrasses are born hermaphrodites and have the ability to turn into males should the need arise. And it arises often. All dominant male wrasses started their lives as females.

Wrasses born male, however, are not hermaphroditic. They're stuck with being minor males for life with little chance of reproducing.

In some wrasse species, dominant males set up harems. A male defends his harem vigorously and mates with all his females. If this big male dies, the females don't wait around for another male to show up. The largest female in the harem changes sex and takes over.

On some large reefs, dominant male wrasses set up territories and jealously guard these against other males. And for good reason. At around noon each day, females of this species cruise the reef looking for these mating stations and stop at the one guarded by a good-looking male.

On average, these lucky males spawn about 40 times a day. In areas crowded with wrasses, these guys can discharge sperm up to 100 times a day.

Other types of wrasses mate in groups. The action begins when a female rushes upward toward the water's surface, ejecting eggs. Males charge in from all directions and spew sperm in the vicinity of the eggs.

I've had the good fortune to watch wrasses do this impressive spawning dance. It looks like a fish version of water ballet.

Besides changing sex, wrasses also change colors and patterns. I'm not talking shades of gray here. Some juvenile wrasses don't remotely resemble adults of their species, and some males don't look anything like their females.

A wrasse well known among divers for its remarkable color differences is the yellowtail coris, also called the rainbow wrasse. Juveniles of this species are bright red with several white saddles running down their backs. These stunning fish, although only a few inches long, are hard to miss. In fact, this juvenile wrasse is the one my dive buddy remembered the most vividly after our recent dive.

As they grow larger, these red fish begin to turn into living rainbows of blues, greens, reds and yellows. Most rainbow wrasses live their entire lives in this colorful garb. Some females' fate, however, is to replace dominant males. These transsexuals turn dark in color, change patterns and grow big, about 15 inches long.

It's easy to see how the wrasses perplexed early biologists, who sometimes counted different growth phases of a wrasse as different species.

Even today, with detailed descriptions and excellent photos, it's hard to sort out 43 species all going through various color, pattern and size phases. As a result, even trying hard, some of us still can't tell our wrasses from a hole in the ground.

Happy wrasse watching.



Marine science writer Susan Scott's Ocean Watch column
appears weekly in the Star-Bulletin. Contact her at http://www.susanscott.net.



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